Square Enix FFXI and Formatting HDD

My question is can it be done?

From all ive read in the manual, there is some crucial data sotred in the HDD that, if wiped, wont be able to be reinstalled due to the one-time only CD Key (like keys, user names and passwords).

But ive also read that you can simply uninstall the program, and the PC will retain this crucial data, just delete and reinstall the rest of it.

Obviously, 7.5 gigs is waay to big to be backed up onto a CD; so im wondering if it can be done at all?
I was thinking the only way i could do it would be uninstalling the game, locating this crucial data and backing just it up. But im not even sure where it is; what form its in, and if it can be reinstalled on the Hard Drive..

Basically, aol sucks. and ill be very anooyed if i have to spend andother 70 bucks on a new copy, and start with a new character (!) just because aol lets in viruses up the ying-yang XD

So, can anybody help me? I believe the same problem would be experienced with Unreal 2004, if thats any help...